Relay plunger



April 8, 1958 J. K. LENTZ RELAY PLUNGER Filed Dec'. 3. 1956 Jo/zjle BY al 2 l A m im v er.

United States Patent O 2,830,153 RELAY PLUNGER Joseph K. Lentzi,Elkhart, Ind., assignor to Durakool, Inc.,

lkhart, Ind., a corporation of Indiana Application December 3, 1956,Serial No. 625,715

9 Claims. (Cl. 200--112) This invention relates generally to mercuryrelays and more particularly to improvements in plunger assembliesthereof.

Mercury relays having a magnetic plunger floating in a body of mercurywithin an enclosed electrode casing have been known and used for sometime. In the operation of such a mechanism, the plunger assembly isselectively raised or lowered by energizing a solenoid coil or likemeans to displace the body of mercury and establish contact between apair of electrodes, one Vof which normally constitutes the outsidecasing of the relay assembly, and the other which normally extendscoaxially into the interior o'f such casing.

Past plunger assemblies have normally constituted a metal shell orsleeve in which is mounted ceramic means including a cup portion forcontaining a body of mercury. Usually the ceramiccontains passagewaysfor the ow of mercury through the plunger and valve means are sometimesemployed to control the rate of such flow to regulate the rate of ascentand descent of the plunger and the operating characteristics of therelay. Heretofore such plunger assemblies have been plagued by atendency to pick up mercury in small crevices existent between the outermetal shell thereof and the internally disposed ceramic. When themercury is entrapped in between the several parts of the relay plunger,such plunger gradually assumes a diiferentweight characteristic, whichchanges its lloatingr position Within the body of mercury. Over a periodof time the floating characteristics of the plunger may change enough todestroy the operational characteristics of the relay and in particularto destroy or vary the timing for the operation of the plunger. Whilevarious attempts have been made in the past to avoid this undesirableresult, a successful solution to the problem has heretofore goneundetected.

' tight seal or junction between the ceramic and metal portions of theplunger. Thus, I prevent mercury from entering crevices or spacesbetween the ,parts of the plung- With the plungerconstructed accordingto the con- Icepts and features of my presentinvention, the initial-design characteristics and particularly the floating or sinkingoperation of the plunger india body of mercury is maintained ata'constant value thereby insuring predetermined` operationalcharacteristics for the relay.

To 'accomplish the results of my invention, I propose 1 to insert alayer of glass or other fusible material between the ceramic and metalportions of the relay plunger,

which glass or ceramic is suitable fused in manufacture to provide asealed bond between the parts to prevent the entrapment of mercury. Asthere are no interstices between ceramic and metal member in my improvedcon- The main object of thisv invention is to provide a new and improvedplunger assembly for amercury relay.

2,830,153 Fatented Apr. 8, 19.58

Still another object of my invention is to provide a new and improvedplunger assembly for mercury relays in which a sealed or fused bond isprovided between the metal and ceramic parts ,of the plunger to preventthe entrapment of mercury therebetween.

Still another object of my invention is to provide a new and improvedplunger for a mercury-relay in which the parts are so fused and bondedtogether that entrapment of mercury by the plunger is successfullyavoided. .Y

Still another important object of my invention is to provide a plungerfor a mercury relay having a metal shell bonded to a ceramic member by asuitable bonding agent, in which the bonding agent is maintained undercompression under normal operating temperatures.

The aboveand further objects, features and advantages of this inventionwill appear to those familiar in the art from the following detaileddescription and specifications of the several embodiments thereofillustrated in the accompanying drawings.

In the drawings: j Y

Figure lis a crosssectional view taken substantially along thelongitudinalcenter line of a typical relay plunger embodyingk"theconcepts and teachings Vof this invention; 1

Figure 2 is another cross-sectional View similar to Figure lillustrating the features of'a modified plunger ernbodying the presentinvention; a

Figure 3 is still another cross-sectional view similar to Figure 1illustrating a'third form of plunger assembly embodying the concept ofthe present invention; and

Figure 4 is another cross-sectional Viewv similar to Figure l showing astill further modified form of plunger in which the teachings of mypresent invention are employed. l n Y Turning now to the'features oftheplunger illustrated in Figure 1 of thedrawings, it will be recognizedthat the plunger assembly, indicated generally by 'numeral 10 therein,comprises an outer metal sleeve 11 formed as asubstantially cylindricalmember. Disposed internally of the upper end of sleeve 10 is an arcshield means formed by a first ceramic member 12 according toconventionaly practice. Ceramic 12 coaxially receives an upwardlyprojecting cup portion 13 of a second ceramic member 14 which extendssubstantially to the lower end of the shell 11. An annular spacer ring15 is provided between the lower end of ceramic 14 and a bumper disc 16mounted within the'lower end of shell 11. Shell'11 is turned over as at17 to hold the bumper disc, spacer ring and ceramic members in assembly.The upper end of shell 11 is likewise turned inwardly in a substantiallyfrusto-conical formation asV at 18 tol tie the arc shield ceramic 12within the interior confines of the shell 11. In. this latter respect Ait will be understood that arc shield member 12 has .an upwardlyextending neck portion 20 which projects upwardly and outwardly 4throughthe opening provided by the truste-conical portion 18 of shell casing11'.v

` A rst glass seal 21 is disposed between sloping shoulder portion 22 ofceramic 12 and the inside face of the inwardly turned portion 18 at. theupper end of shell 11. Such bead or seal member 21 is suitably fused inassembly to bond ceramic 12 to shell 11 adjacent the upper end thereof.Asecond annular glass Vseal bead 24 is likewise disposed-adjacent thelower end of ceramic 12 so as to extend around ceramic 12 and beneathits lower end. The annular bead 24 extends between ceramic member 12,the interior face of the shell 11 and an inwardly set shoulder portion25 of the ceramic 14. Bead 24 is likewise fused Vin final assembly toprovide a fusion bond between the shell 11 and the two ceramic members12 and 14.

yof thermal expansion in the order of 86X 10-7.

While ceramic 14 is shown in cross section, it is to be understood thatsuch contains suitable ports or passageways 26 permitting thepassage ofmercury upwardly through the interior of shell 11 so that the same mayenter the hollow cup portion 13 of ceramic 14. This construction isaccording to `conventional and known practice with the flow of mercurybeing regulated by i ports 27 formed through the bumper member 16.

f outstanding importance in the assembly 10 of Figure l is the provisionof suitable materials having cociiicients of expansion adapted to carryout a unique feature of the present invention in which the glass beadmembers 21 and 24 are maintained in a substantially compressed conditionto form a compression seal. This is carried out by constructing theouter metal shell 11 from a suitable metal, such as cold rolled steel,having a coeiiicient of thermal expansion in the order of l30 107, forexample. The glass beads 21 and 2a are then made of any suitablecommercially available product for this purpose having a lessercoefficient of expansion than the metal 11 as in the order of 89x10-Fland a fusion point of approximately 1000 F. The ceramic members 12 and14 are preferably constructed of Steatite or a like commercial producthaving a coeicient In the normal operation of a device of thischaracter, the arc shield ceramic 12, as well as the cup portion 13 ofceramic 14, are subjected to high temperatures at the ilash caused atmake and break of circuit through the relay. It would appear from theexpansion coefiicients noted hereinabove that the metal having a greaterrate of thermal expansion than the glass and ceramic would not permitthe compression of the glass between ceramic and metal. However, havinga greater rate of expansion than the ceramic or glass, the metal alsohas a greater rate of contraction. In the inital manufacture the glass,ceramic and metal are heated to a temperature of approximately l800 F.,which is morethan adequate to fuse and seal the glass to the ceramic andmetal, since the same has a fusion temperature of around l000 F. asnoted above. As the assembly cools after fusion of the glass beads 21and 24, the glass sets up at approximately 1000D F. while the metalsleeve 11 continues to contract faster than the glass and ceramic,therefore, placing the glass under compression as the cooling proceeds.YIn most normal operations of the plunger thel operating temperatures donot exceed 1000 F. so that the initial compression of the glass is notrelieved even though it is reduced as the metal is heated from the arcor ash at make and break of circuit through the relay. If the heating ofthe relay plunger at any time exceeds the fusion temperature for theglass, the latter becomes plastic again, but upon succeeding cooling theabove described cycle for providing a compression seal is repeated.

I have found that a plunger constructed according to the. concepts laid`out in Figure l is most successful in substantially preventing theentrapment of mercury be- -tween the ceramic member 1.2 and metal shell11. The

provision of the two-spaced glass beads 21 and 24 acting as acompression seals suitably maintain their sealed integrity throughoutthe operating temperatures of the device to prevent the entry of anymercury in the spacing 30 surrounding ceramic 12.

Turning now to the aspects of a modiiiedv plunger assembly a shown inFigure 2, it will be recognized that the same includes an outer metalshell 31,. an arc shield ceramic 32 receptive of a central cup. portion33 associated with a second ceramic member 34. As in the assembly 10first described, the shell 31 is turned over at its lower end, as at 35,in anV annular fashion, and at its upper end, as at 36, to hold the'ceramic members against longitudinal displacement. First and secondglass@ bead members 37 and 3S are provided adjacent the upper and lowerends, respectively, of the arc shield ceramic 32 to fuse such ceramicmember to the interior side walls or" shell 3l. A spacer ring 39 isprovided between the lower end of ceramic 34 and a bumper plate 40 whichormulates the extreme or lowermost end of the plunger assembly. It willbe recognized that the assembly of Figure 2 differs from that of Figurel in that the lower end of the arc shield ceramic 32 rests againstshoulder portion il of the second ceramic member 34 with glass beadserving to bond both of said ceramics together opposite their point ofjunction, as well as joining these members to the interior side walls ofthe metal sleeve 31. By comparison with the structure of Figure 1, bead24 in that figure serves to hold the shield ceramic 12 in a spacedrelation relative to the lower or second ceramic 14. Although both thebeads 24 and 38 of Figures l and 2, respectively, serve to bond the twoceramic members one to the other, as well as to the inside face of themetal sleeves involved, the modified form of Figure 2 is thought to be asomewhat more stable structure than that of Figure l, since the twoceramic members are engaged in abutting relationship as shown and are,therefore, longitudinally fixed within shell 31.

From Figure 2 the cross-shaped configuration of the second `ceramicmembers 34 will be recognized, the same comprising plural finger walls42 extending outwardly from a central cylindrical core portion 43 toprovide necessary passageways for the mercury to flow upwardly to theinterior of the cup formed by the portion 33 of ceramic 34. Thecross-shaped configuration employed in ceramic 34 is likewise suitablyemployed for ceramic 1li of the device in Figure l to provide thenecessary mercury passageways as previously related.

Turning now to the features ofthe second modified form of plunger 10b,illustrated in Figure 3, it will be understood that such assemblyincludes an outer metal sleeve 50', a first arc shield ceramic 51disposed near the top of sleeve 50 and coaxially of a second ceramic 52.Ceramic 52 has a central cup portion 53 adjacent its upper end whichextends into the hollow interior of the arc ceramic 5l. The remainingportion of the assembly is as before described with ceramicv 52 beingspaced from the lower end of an inwardly turned ange portion 54 of thesleeve Si) by means of an annular spacing ring 55. The lower end of theplunger assembly is defined by a bumper shield 562 The upper end ofsleeve 50 is turned inwardly as at 57 to embrace the upwardly extendingopen threat portion 5S of the arc ceramic member 5l. To provide a sea-lbetween the two ceramic members and the metal sleeve, a glass'bead 60isemployed, the same extending from shoulder portion 61 of the lower vorsecond ceramic 52 concentrically about the exterior walls of the shieldceramic 51. In this respect, it will be noted that glass bead 60completely envelops all the portions of the shield ceramic 51 whichreside within the interior of thc metal sleeve 50.

The structure illustrated. in Figure 3 is improved over that of Figuresl and 2 because of thecontinuous annular nature of the bead 60since suchprovides a solid construction from the exterior of the metal sleeve tothe interior of the shield ceramic .51, thus to give stability againstshock and to increase the area of the seal. The increased seal areaeffectively prevents liquid, such as mercury, from lodging between theceramic 60 and corresponding to the ceramic members 14, 34 and 52,previously described. The glass bead or envelope 71 likewise bonds witha spacer ring 73 adjacent an inwardly turned flange portion 74 and abumper 75 at the lower end of the plunger assembly. Bead 71 also isfused to the inside walls of the metal sleeve 70. In this particulararrangement it will be appreciated that the entire internal surface ofthe plunger is concealed by the presence of the glass envelope 71 andthat the structure therein is simplified over those of Figures 1, 2 and3 by the elimination therefrom of the arc or shield ceramic membernormally disposed in the upper end of the metal sleeve. In this respect,the glass envelope itself acts to shield the metal of the sleeve 70 fromthe effects of arcing at the make and break of contact in the plunger.Preferably, to withstand high temperatures and etchingj the glass ofenvelope should be of a synthetic quartz type having a coefficient ofexpansion less than the cold rolled steel used for sleeve 70, oralternatively a Steatite ceramic liner can be used in place of the glassliner 71, for example, Steatite No. 196 manufactured by American LavaCompany, Chattanooga, Tennessee. It will also be noticed that theassembly if Figure 4 provides full sealed engagement between glass 71and the surfaces of ceramic 72 contacted thereby.

In the above described forms of the invention, it is a feature common toall that the glass seal or bead members have a coefiicient of expansionless than that of the outer metal shell. By this arrangement, normaloperating temperatures occurring within the plunger, cause the glass tobe maintained in a compressed state to enhance its sealed relationshipwith the outer metal sleeve irrespective of its fusion connection withthe outer metal shell and the ceramic members involved. By so providingthe sealing medium under compression at all times during normal usage, Iam assured against the entrapment of mercury or similar liquids betweenthe several parts of the assembly.

It is believed that those familiar with the art will recognize thepresent invention as a marked advancement in the art. While I haveherein shown and described the features of my invention in conjunctionwith four typical embodiments thereof, it is to be appreciated that thenumerous changes, modifications and substitutions of equivalents may beresorted to therein without necessarily departing from the spirit andscope of my invention. As a consequence, it is not my intention to belimited to the particular forms of my invention herein described andillustrated except as may appear in the following appended claims.

I claim:

1. In a plunger assembly for mercury relays and the like, thecombination comprising, a tubular metal shell member, an insulatormember mounted coaxially within said shell member, and seal meansdisposed between said two members under compression therebetween andmaking a fused bond therewith.

2. In a plunger assembly for a mercury relay, the combinationcomprising, a substantially cylindrical ceramic member, a metal shellmember concentrically surrounding said ceramic member, an annular glassseal means disposed between said ceramic and shell members to preventthe entrapment of mercury therebetween, said glass seal means havingfused connection with said two members and being maintained undercompression therebetween in the normal operating temperature range forthe relay.

3. In a plunger assembly for a mercury relay, the combinationcomprising, a substantially cylindrical ceramic member, a metal shellmember concentrically surrounding said ceramic member, an annular glassseal means disposed between said ceramic and shell members to preventthe entry and entrapment of mercury therebetween, said glass seal meanshaving a smaller coefficient 6 of thermal expansion than said metalshell member whereby the same is held under compression by said metalshell member between the latter and said ceramic member in the normaloperating temperature range for the relay.

4. In a plunger assembly for mercury relays and the like, thecombination comprising, a substantially cylindrical ceramic member, anouter metal shell member surrounding said ceramic member, and seal meansdisposed between said ceramic and metal shell members for maintainingthe same in concentric disposition, said seal means being maintainedunder compression and having fused connection with said shell andceramic members.

5. The combination as set forth in claim 4 in which said seal meanscomprises glass having a smaller coefficient of thermal expansion thanthe metal of said shell member whereby the same is held undercompression by said shell metal at temperatures below the fusion pointof said glass.

6. A plunger assembly for use in a tubular body of a mercury relay todisplace mercury contained therein, comprising, a tubular open-endedmetal shell, a first insulating member mounted coaxially within theupper interior of said shell, a second insulating member mountedcoaxially within the lower interior of said shell and having meansdefining a passageway for mercury, a first annular compression sealmeans bonding the upper end of said first insulating member to theinside walls of said shell, and a second compression seal means bondingthe lower end of said first insulating member to the upper end of saidsecond insulating member and the inside walls of said shell at a pointintermediate the ends of the latter, said two compression seal meansserving to prevent the passage and entrapment of mercury between saidfirst insulating member and said shell.

7. A plunger assembly for use within a tubular body of a mercury relaycomprising, a substantially tubular open-ended metal shell, aninsulating member mounted within the interior of said shell and adjacentone end thereof, and an envelope of insulating material disposed betweensaid first insulating member and said shell to cover the interior wallsof the latter, said envelope having fused connection with the insidewalls of said shell and the exterior walls of said first insulatingmember thereby to effectively seal said first insulating member to saidshell and prevent the entry and passageway of mercury therebetween.

8. The combination as set forth in claim 7 wherein said envelopecomprises glass having a lower coeicient of thermal expansion than themetal of said shell such that the latter maintains said envelope underradial compression at temperatures below the fusion point of said glass.

9. A plunger assembly for use in a tubular body of a mercury relay todisplace mercury contained therein,

comprising, a tubular open-ended metal shell, a -hollow' insulatingmember mounted coaxially within the interior of said shell and spacedradially inward therefrom, said insulating member having means defininga passageway for mercury, bumper means disposed at the lower end of saidshell and beneath said insulating member and having port means forcontrolling the passage of mercury, and a vitreous annular seal meansdisposed between said insulating member and said shell and having afused bond therewith, said seal means having a lower coefficient ofthermal expansion than the metal of said shell and a fusion pointsubstantially lower than the melting point of the metal of said shellwhereby the same is radially compressed by said shell at temperaturesbelow its said fusion point.

References Cited in the file of this patent UNITED STATES PATENTSCianchi May 9, 1939

